A schema variant is an object that can hold a single piece of data of a particular type. That data can be assigned a new value or the same or different type.
The fundamental types are:
Type
Description
Function to set
bool
A standard C++ boolean type with true and false values
To create a schema variant you call SchemaVariantCreate followed by a call to set some data into it with the appropriate function. Until you have set data into the newly created schema variant the type of the schema variant will be SystemType::Undefined. Calling schema variant functions on undefined schema variants may fail.
When you are finished with a schema variant call SchemaVariantDelete to free the schema variant.
Example
Setting/Changing
You can set/change the value and type of a schema variant with the following calls
When setting the schema variable to an object pointer you specify the type of the stored object in the function call. This can be a TypeHash of your construction or one pre-defined types if the object you are storing matches the type. e.g
Type
Object pointed to
SystemType::Byte
unsigned char
SystemType:Char
char
SystemType:;DateTime
Qbik private
SystemType::Int16
Signed 16 bit integer
SystemType::Int32
Signed 32 bit integer
SystemType::Int64
Signed 64 bit integer
SystemType::IP4Address
Qbik private
SystemType::UInt16
Unsigned 16 bit integer
SystemType::UInt32
Unsigned 32 bit integer
SystemType::UInt64
Unsigned 64 bit integer
SystemType::Single
Single precision float
SystemType::Double
Double precision float
SystemType::String
std::wstring
SystemType::StringA
std::string
Example
Classes
Sometimes the schema framework may need to call functions for a schema variant in order to perform operations like casts. This may require the schema framework to know what class the schema variant belongs to. If you will need to perform class based operations on your schema variants then you should set a schema class for the schema variant by calling SchemaVariantSetSchema
Coercion
Coercion of schema variants is the act of forcing a schema variant to another type. The schema variant set functions (SchemaVariantSetBool etc) perform a coercion to the requested type before setting the value. The rules for coercion are as follows.
If the requested type is the same as the schema variant type then no change to the schema variant occurs
If the requested type is different to the schema variant type and the requested type is one of the standard types (Undefined, ANumber, AString or Boolean) then the type is changed and the value of the variant is set to the default for that type.
If the requested type is any other type the type of the schema variant is changed but the value is not